Starter relay

SOURCE: 1995 golf won't start.

check power at starter solenoid if you got power you need a starter motor if not check power at ignition switch .....................

SOURCE: 98 jetta wont start with a good battery and good starter

A common plroblem on the 2.0 engine cars is the distributer, try changing that, if that doesnt work their is a sensor in the block right behind the oil filter than can cause the no start issue, but its not as common

SOURCE: Volkswagen passat 96 AC relay location

You should never connect a 12volt to the compressor solenoid.unless you unplug it first, because on some cars the ac solenoid is driven by an electronic circuit. Semiconductors are very sensitive to excessive current. I once had to repair the computer on a mercedes because the other mechanic did that. Luckily I know how to repair electronic circuits, or they would have bought a 500 dollars computer the little chip that blew only costed a dollar fifty cents at radio shack,.LOL. Anyways back to your problem, Have you checked if there is a leak, and all the refrigerant might have leaked out? This would prevent the compressor from coming on. Along the ac line there is a switch, sometimes by the reciever drier, when the system looses refrigerant the pressure inside drops and that pressure switch disable the compressor. , and the compressor wont come on. This is to protect the compressor, because it will be damaged if you run it without refrigerant. Ac clutch solenoid is usually is not driven by relay, because an ac solenoid don't really take much current to to kick in, unless of course it is shorted. It would either be directly from the inside switch usually in series with the fan control or driven by a small transistor in a circuit, and the electronic circuit is driven by the ac controls inside. I think the problem with your ac is that it has no refrigerant thats why the compressor wont come on.

SOURCE: 1996 VW jetta will not start

You vehicle works off a standard ignition key which links to a electrical ignition switch. The wire from the switch goes to the starter solenoid. That wire has a fusable link which operates like a fuse. If to many amps surge through this wire it will melt down inside the insulation. The insulation will not melt away causing a headache to most novice mechcanics. Pull on the solenoid wire a few inches away from the solenoid and see if it stretches at least 1/8 of an inch or more. If it does it has an open stopping the continuity to the positive lug to the solenoid preventing it to work. Any auto parts store sells these fusable links. The counterperson will suggest the crimping supplies and tools needed to purchase for this repair

SOURCE: locate Relay no. 30

Above fuse box, accessed by removing driver side kick panel (cover above pedals).